Drift in South Dakota. — Todd. 99 
of a cervical vertebra of a large vertebrate; fragments of 
lurtle-shell, resembling the common mud-turtle in appearance 
and size, and two or three small bones, apparently of an 
animal about the size of a rabbit. The visit was brief, and 
further investigation would doubtless reveal more fossils. The 
vertebrate remains were submitted to Prof. William B. Scott, 
of Princeton, who determined the largest to be a cervical 
vertebra of a horse. The other bones were undeterminable. 
Through the thoughtfulness of Mr. Bain, a series of the 
shells was submitted to Professor Shimek, in time to have his 
determinations for this paper. His report is as follows: 
"The following are from the Illinois Central railroad cut 
east of Sioux Falls, S. D. : 
"I. Planorbisbicarinatus Say. 
"2. Planorbis parvus Say. 
"3. Physa heterostropha (Say) Say. 
"4. Limnea caperata Say. 
"5. Valvata tricarinata (Say) Say. 
"6. Sphoerium sulcatum (Lam.) Prime. 
"7. Pisidium compressum Prime. 
"8. Vallonia costata (Miill.) Ster. 
"Of these, one to four are Pulmonates, five is a gill-bearer 
(Prosobranch), six and seven are bivalves, and eight is terres- 
trial. The set one to seven can be duplicated in most of our 
northwestern ponds with muddy bottoms. Eight is terrestrial, 
but grows sometimes near the edges of ponds and is common 
along streams. There is one specimen of this. 
"The other lot from Sioux Falls, S. D., 'near tlie brewery," 
contains two species: Limnea caperata Say, and Planorbis al- 
bus Miill., probably. The specimens are poor. Both of these 
are common in northwestern ponds to-day." 
West of this pond hole the rest of the underlying till had 
apparently had its soil, if ever formed, removed by the erosion 
attending the deposition of the overlying till. Between the 
two tills is a considerable deposit of gravel. The lower till 
was comparatively free from pebbles of any considerable size 
and has been referred to by the writer in his correspondence as 
a pebbleless clay, but more careful examination during the 
recent visit, brought out the fact that it contains small pebbles 
of crystalline rocks evidently of northern origin. In places 
